Li et al. found reduced FRC and diffusion
impairment and this, reduction in static lung volume
was correlated with the degree of obesity [17]. Obese subjects
had a reduction in the expiratory reserve volume (ERV) due
to decreased FRC by the mass loading effect of obesity. This
may be accompanied by regional gas trapping in poorly ventilated
lung units due to small airway closure and subsequent
atelectasis [18]. Biring et al., Jenkins and Moxham concluded
that TLC was normal in both mild and morbid obesity
[18,19]. Guimaraesa et al. found that TLC was normal in obese
persons and was significantly increased after weight reduction
[13]. In contrast, FRC and RV were less than normal levels
and after weight reduction, there was a significant increase of
FRC but insignificant as regards RV [13].